In a floating type brake disk a braking section and a hub section are each a separate unit and are connected to each other so that even when the braking section becomes thermally expanded with heat produced by friction of a brake pad with application of a braking force, such thermal expansion is confined only to the braking section and, on top of that, since the braking section is of a simple ring shape and not bound by the hub section, it does not cause any significant distortion to a brake surface, thus bringing about an advantage that the braking action remains consistent.
In a brake disk of this type, is was usual that a measure of having a dish-shaped spring put in pressure contact with the side surface of each of both sections was taken in order to restrict a relative movement in the axial direction of both the braking section and the hub section with respect to each other and to prevent noise that could result from loosneing of the two sections. (Jikkai Sho 60-3333 is one example thereof.)
In the foregoing prior art, it was necessary to use a dish-shaped spring having a greater spring constant and durability because the load making both the braking section and the hub section move relatively in the axial direction should be supported by resilience of the dish-shaped spring.